Out of nowhere, a cop appears. He grabs the young man and slams his head down onto the bar-code reader.

"Green police!" shouts the cop. "You picked the wrong day to mess with the ecosystem, plastic boy."

The "Green Police" Audi commercial aired during the Super Bowl may not have been the most entertaining, but it was easily the most significant.

Its obvious working assumption: Environmentalism has an authoritarian core, and this is what you'll get if its impulses are left unchecked.

It seemed a dubious way to sell cars, but the ad's subtext was a clear sign of the times. Environmental concerns are on the ebb: In a poll by Pew Research Center on 2010 priorities, the environment ranked only 16th out of 21 topics. Global warming? Dead last.

For the environmental movement, this is bad news. Not only is it tough to raise awareness when the economy is in the tank, now you have a wave of doubts enveloping the theory of man-caused global warming — the movement's primo catastrophe product since the 1980s.

The Climategate e-mails made public late last year provided a loose thread on which skeptics are now eagerly pulling. The e-mails showed climate scientists discussing how to bully editors, thwart freedom-of-information requests, block data-sharing requests and distort the peer-review process.

That kicked open the door for contrary views, and a lot of credentialed people who doubted the theory, or some of the particulars, began to get a hearing. Others began picking through one of the theory's sacred texts, the 2007 report by the U.N.'s Intergovernmental Panel on Climate Change, and found some embarrassing pratfalls.

For example, the panel predicted that Himalayan glaciers would melt away by 2035, a forecast that turned out to be groundless. Defenders said no big deal: The glacier data weren't in the carefully reviewed Synthesis Report, where the panel issued its recommendations to world leaders.

But the Synthesis Report did include another headline-grabber — a prediction that by 2020, rain-fed North African crop production could plummet by 50 percent.

Wrong, according to a recent story in the London Times. Chris Field, lead author of the panel's climate impact team, told reporters he finds "no evidence" to support that assertion. But that hadn't stopped the panel's leader, Rajendra Pachauri, and U.N. Secretary General Ban Ki-moon from citing the unsupportable finding in speeches. (I found all this at Walter Russell Mead's blog at the-american-interest.com, a good place to follow developments on this front.)

Climategate hasn't yet proved that man-caused global warming is a fraud. But the flap has swept away any political warrant claimed by the greens to "change the way we live" through cap-and-trade schemes or heavy-handed regulation of carbon dioxide.

One of the problems the environmental movement has — the reason so many people run hot and cold on its concerns — is that many of the greens don't like people, literally. The human race, they say, is a virus on the planet. Or a cancer. Or the "AIDS of the Earth."

Not surprisingly, every so often a lot of people decide that the polite thing to do is simply move environmentalists and their apocalyptic terrors to the bottom of the priority list, and ignore them for a while.